A Precise Diagnostic Method for Problem Segments in 0.4 kV Low-Voltage Distribution Areas Based on Voltage-Drop Analysis

To overcome the prevalent drawbacks of blind remediation, poor location accuracy and low efficiency in solving low-voltage issues in 0.4 kV networks, this paper proposes a voltage-drop-based method for accurately identifying problematic line segments. First, the three-side (supply, distribution, customer) causes of low voltage are systematically analysed and the key difficulties in remediation are examined. On this basis, a voltage-drop calculation model for low-voltage lines is rigorously derived, and a novel location logic centred on "comparison of theoretical vs. actual voltage drop" is introduced. By processing the substation′s head-end voltage and current data together with customers′ end-point voltages, a diagnostic model that can identify the equivalent impedance of abnormal segments is built, enabling the shift from area-wide screening to pinpointing specific problem segments. A field case study shows that the method can rapidly and accurately locate the critical segments responsible for low voltage (e.g., undersized conductors, poor contacts) with a diagnostic accuracy above 95%, and raises remediation efficiency by roughly 70% compared with traditional full-line inspection.